Alexander l



STATES PATENT OFFICE.

' ALEXANDER L. HOLLEY, OF NEW7 YORK, N. Y.

VARIABLE CUT-OFF GEAR FOR STEAM-ENGINES.

Specification of Letters Patent No. 23,684, dated April 19', -1859.

To all whom 'it 'may concern:

Be it known that I, ALEXANDER L. I-IOLLEY, of the State, county, andcity of New York, have invented a new and Improved Method of Eecting aVariable Cut-Off for Steam-Engines; and I do hereby declare that thefollowing is a full and exact description thereof, reference being hadto the accompanying drawings and to the letters of reference markedthereon.

The nature of my invention consists in the combination of the motion ofan eccentric, with the motion of a supplementary steam piston, toproduce such a motion of the main valve, as shall rapidly open theinduction end of said valve, with any desirable lead, and close the sameand instantly at any desirable portion of the stroke of the main piston,without closing the exhaust end of said valve till the main piston hasnearly completed its stroke.

The accompanying drawings Figures 1 and 2 show the application of theabove valve motion to the ordinary locomotive engine, Fig. 1 being aplan, and Fig. 2 a side elevation.

The same letters refer to like parts.

To enable others skilled in the art to make and use my invention, I willproceed to describe its construction and operation.

The eccentric rod D from the eccentric A moves the lower arm of thelever E F by the hook G. To reverse the engine, the hook H on the sameeccentric rod D is connected with the pin F of the lever E F by means ofthe reverse shaft I, in the ordinary manner.

The lever E F is attached to and moves the rock shaft J, which moves thelever K, which moves the lower end of the lever L M. The supplementarysteam piston B is attached by its rod Q to the lever L M at N, and thevalve stem O of the main valve C is attached to the same lever at M. Theeccentric rod D, may if convenient be attached directly to the lever L Mat L, thus dispensing with the lever E F and the rock shaft J. Also, aseparate eccentric may be used for reversing. Also the valve stem O maybe arranged to take hold of the lever L M below the piston rod Q, andstill perform the same functions. It is here attached above the rod Q togive the piston B a short stroke, thus avoiding its slamming o by greatmomentum.

The motion of the piston B may be arrested at the end of its stroke byany of the ordinary methods. It is here arrested by the disks R S whichare secured to the piston rod Q) coming in contact with the rubber disksc c. The commencement of the motion of the piston B is accelerated, andthe close of its motion is retarded by the springs T U.

Steam is admitted to the piston B by the ordinary valve motion,consisting of the valve c, valve rod f, rock shaft g eccentric rod L andeccentric z'. The eccentric z' may be turned forward or backward on themain shaft V to vary the time of the opening of the valve c, and hencethe time of the cut-o of the main valve C by any of the ordinarymethods, or the valve c may be driven by tappets from the cross head W.The eccentric z' is here moved forward and backward as follows viz: Theeccentric z' is secured lto and turns with the gear wheel 7c which isrevolved on the shaft V by the gear wheels m n, which are turned by thegear wheel 0, which isy secured to, and turns with the shaft V.

The ring p which is loose on the shaft V holds the wheels m n in theirplaces. The ring p, being moved forward or backward by the rod g and thelever r, it moves the wheel 7c and the eccentric z' backward or forward,thus varying the time of the opening of the valve c. works thesupplementary valve of the other main steam engine of the locomotive, isfastened to and wo-rked by the same wheels lc m n 0.

The operation of the engine is as follows, viz: The piston P standing atthe back end of its stroke as shown in the drawing, the valve C is setwith the desirable lead. The piston P moving forward, the lower end ofthe lever L M moves backward, and the upper end of L M moves forward,opening the valve G. At any point during the stroke of P, at which thesmall valve c shall have been set to open, steam entering the port udrives the piston B back, which moves the valve C over the port o, but(in cutting olf y late in the stroke), does not close the exhaust portfw, which port is closed near the end of the stroke by the motion of theeccentric A. If the port w is closed, as it will be at the time of a cuto occurring early in the stroke, it is immediately reopened and heldopen till near the end of the stroke by the motion of the eccentric A.

The eccentric s which- The closing of the exhaust port, however, duringthe cut-off at any point, may be prevented by a wider opening of thecavity of the valve C at the cost of a slightly premature exhaust.

The simple motion of a steam piston, or any motion derived from themotion of the main steam engine, cannot be so applied to a valve as toenable it to perform the above functions, without considerablecomplication of parts; also, the motion of a steam piston appliedinstead of an eccentric for opening a rapidly moving valve, may not opensaid valve so exactly as to time, as to preserve a uniform lead. Aslight variation in the cut off however, should such variation occur isof no practical account.

The advantages of this improvement are, lst. The ports are entirelyopened before the valve cuts olf at any portion of the stroke of thepiston, which prevents wiredrawing and waste of steam by friction. 2d.The cut-o of the steam is instantaneous, which prevents wire-drawing.3d. A cutoif may be obtained at each point of the stroke f the piston.4th. An injurious amount of compression or cushioning of steam Visprevented. 5th. Premature exhaust is prevented. 6th. Since the lead isgiven to the valve by the supplementary piston, no lead is required onthe eccentric, and hence one eccentric may be used for the forward andbackward motion of the engine. 7th. The large parts of the valve motionare simple in construction and few in number, which will prevent unduerepair expenses.

I disclaim the method described of moving the supplementary valve e, thesame being in use.

I disclaim the use of a supplement-ary steam piston as the sole mover ofa valve.

I claim- Such a combination of the motion of an eccentric or itsequivalent, with the motion of a steam piston for moving a valve, aswill effect a variable cut olf of the induction steam, withoutinterfering with a free exhaust, substantially in the mannerhereinbefore described.

ALEXANDER L. HOLLEY.

JOSEPH A. KENT, S. D. CoZzENs.

